The dollar as a currency unit (especially the US dollar); commonly used in discussions about foreign currency and exchange.
今日の為替で１ドルは約110円だ。
At today's exchange rate, 1 dollar is about 110 yen.
彼は海外出張のために300ドル両替した。
He exchanged 300 dollars for his business trip abroad.
Colloquially used to mean money or cash in general; a casual way to refer to funds.
まとまったドルが必要だから、少し節約しよう。
I need a good amount of cash, so I'll save a bit.
彼はドルに興味がなく、貯金は別の通貨でしている。
He isn't interested in dollars and saves in another currency.